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ICSE Class 8 Biology Question 4 of 16

The Circulatory System — Question 6

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Question 2

Name any four heart-related conditions that occur commonly in humans. Briefly explain the cause and symptoms of each of them.

Answer

The four heart related conditions common to humans along with their cause and symptoms are given below:

  1. Palpitations — When the heart beats too hard or too fast or sometimes even skips a beat, it is called Palpitations. Palpitations are often caused due to stress or anxiety. Sometimes, certain types of food may also cause Palpitations.
  2. Hypertension — This is a condition that occurs when blood flows through the blood vessels with a force greater than normal. This is also called High Blood Pressure. Hypertension can also strain the heart, damage blood vessels and increase the risk of heart attack or stroke.
  3. Heart attack — A heart attack is a sudden interruption of blood supply to the heart. It usually occurs due to a blood clot that prevents the flow of oxygen rich blood to the cardiac muscle. As, a result a part of the cardiac muscle dies and causes a permanent damage to the heart. Some common symptoms of a heart attack include uncomfortable pressure, tightness or squeezing pain in the centre of the chest, discomfort or pain spreading beyond the chest to the shoulders, neck, jaw, teeth or one or both arms, shortness of breath , dizziness, sweating and nausea.
  4. Cardiac Arrest — A cardiac arrest occurs when the heart suddenly stops pumping blood around the body. In cardiac arrest, a person suddenly loses consciousness and stops breathing or may have abnormal breathing. Some people experience chest pain, shortness of breath, or nausea before a cardiac arrest occurs. The common cause of cardiac arrest is coronary artery disease wherein the walls of the arteries thicken as a result of fat or plaque deposition. Less common causes include major blood loss, lack of oxygen, low potassium levels, heart failure and intense physical exercise.
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Biology | Chapter 8: Circulatory SystemWeb Content

Circulatory System – Interactive Study Guide

Quick Overview

The circulatory system transports blood, oxygen, nutrients, and hormones throughout the body. It consists of the heart (pump), blood (transport medium), and blood vessels (pipelines).

Blood Components

ComponentFunctionKey Fact
Plasma (55%)Transports dissolved substances90% water, carries nutrients, hormones, waste
RBCCarry oxygenBiconcave disc, no nucleus, contain haemoglobin
WBCFight infectionsHave nucleus, larger than RBC, immune defence
PlateletsBlood clottingCell fragments, no nucleus

Blood Group Quick Reference

ABO System

O = Universal Donor (no antigens) | AB = Universal Recipient (no antibodies)

GroupAntigenAntibody
AAanti-B
BBanti-A
ABA & BNone
ONoneanti-A & anti-B

Heart – Quick Facts

  • 4 chambers: RA, RV, LA, LV
  • 4 valves: Tricuspid (R), Bicuspid (L), 2 Semilunar
  • Septum divides right (deoxy) from left (oxy)
  • Left ventricle = thickest wall

Double Circulation

Two Circuits

Pulmonary: RV → Pulmonary artery → Lungs → Pulmonary veins → LA

Systemic: LV → Aorta → Body → Vena cava → RA

Blood Vessels Comparison

ArteriesVeinsCapillaries
DirectionAway from heartTo heartConnect A to V
WallsThickThin1 cell thick
ValvesNoYesNo

Self-Test Questions

Test Yourself
  1. Why is the left ventricle wall thicker than the right?
  2. Draw and label the human heart.
  3. What is double circulation? Describe both circuits.
  4. Why is blood group O called universal donor?
  5. What is the function of valves in veins?

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